In modern cars it is essential to minimize the space occupied by each of the car components, especially under the hood, since the number and complexity of not the least auxiliary equipment needed has increased during the last decades and the design of the car leaves limited space. Many components have therefore been designed to share the space effectively under the hood, especially components being more or less cooperating with each other.
The demand for both comfort and durability has also increased, encouraging the engineers to find solutions both to noise elimination and to wear problems.
Two component types that have been redesigned in parallel in order to save space, both being mounted on the same crankshaft end, include on the one hand torsional vibration dampers, TVDs, and on the other hand belt pulleys for driving auxiliary equipment like generators, water pumps, a/c pumps and servo steering pumps. They thus can come as an assembly, ready to be mounted on the end of an engine crankshaft as one component.
The above mentioned two components can be relatively tightly arranged adjacent each other, but since a modern belt pulley intended to drive auxiliary components from the crankshaft is equipped with means for dampening or decoupling the vibrations and oscillations of the crank shaft from the belt and the auxiliary equipment, the TVD and the belt pulley must leave a little space in between, allowing the belt pulley to change its rotational angle relative to the TVD. There is a cavity between the two components in the assembly, and the cavity can be the source of noise within the hearing range for a human being when the engine is running. In order to dampen noise from this type of assembly it is known to place caps or houses over the entire assembly, a non-wanted space consuming car component.